Project description:Dystonia is a common feature in spinocerebellar ataxias (SCAs). Whether the presence of dystonia is associated with different rate of ataxia progression is not known.To study clinical characteristics and ataxia progression in SCAs with and without dystonia.We studied 334 participants with SCA 1, 2, 3 and 6 from the Clinical Research Consortium for Spinocerebellar Ataxias (CRC-SCA) and compared the clinical characteristics of SCAs with and without dystonia. We repeatedly measured ataxia progression by the Scale for Assessment and Rating of Ataxia every 6 months for 2 years. Regression models were employed to study the association between dystonia and ataxia progression after adjusting for age, sex and pathological CAG repeats. We used logistic regression to analyze the impact of different repeat expansion genes on dystonia in SCAs.Dystonia was most commonly observed in SCA3, followed by SCA2, SCA1, and SCA6. Dystonia was associated with longer CAG repeats in SCA3. The CAG repeat number in TBP normal alleles appeared to modify the presence of dystonia in SCA1. The presence of dystonia was associated with higher SARA scores in SCA1, 2, and 3. Although relatively rare in SCA6, the presence of dystonia was associated with slower progression of ataxia.The presence of dystonia is associated with greater severity of ataxia in SCA1, 2, and 3, but predictive of a slower progression in SCA6. Complex genetic interactions among repeat expansion genes can lead to diverse clinical symptoms and progression in SCAs.
Project description:Dystonia has been described in various genetically proven spinocerebellar ataxias (SCAs), most often in SCA3, SCA17, and SCA2 patients. In this report, we describe different types of dystonia observed in 5 of our 11 SCA2 patients. All our patients had cranial and/or cervical dystonia with focal or segmental distribution. Except for 1 case with isolated cervical dystonia, all other patients had lower cranial affection of variable severity. Although it is difficult to describe ataxia-dystonia syndrome that would be highly characteristic for SCA2, we suggest that occurrence of dystonia in a patient with slowly evolving cerebellar disease should, besides SCA3 and SCA17, also suggest SCA2 testing. In patients with lower cranial dystonia, especially jaw and tongue dystonia, SCA2 should be considered during the diagnostic workup.
Project description:The ataxia telangiectasia mutant (ATM) protein is a sensor and signal transducer that amplifies and communicates signals of DNA damage further to the mediators of cell cycle arrest, apoptosis, and senescence (p16, p19, p21, BAX etc.) which is modified by the strength of the cellular stress. They are able to act as recognition and signaling proteins because of their kinase activity. Classic ataxia telangiectasia is associated with homozygous mutations of the ATM gene, the complete absence of its kinase activity and/or deleterious ATM gene mutations such as truncation/nonsense mutations, loss of function mutation, non-conservative substitutions, frameshift, and deletions. On the other hand, variant ataxia-telangiectasia (A-T) is associated with the presence of residual kinase activity. We report a six-year-old male patient who presented to us with abnormal neck movements as his initial complaint. ATM gene analysis showed a rare pathogenic variant of the ATM gene. The variant was a homozygous nonsense mutation in exon 2 of the ATM gene that resulted in the formation of a stop codon and premature truncation of the protein at codon 23 in exon 2 (p.Arg23Ter). In conclusion, we report a case of an unusual presentation of classic A-T. We should pursue a long-term follow-up and maintain a low threshold for performing pedigree analysis and genetic testing in pediatric patients with movement disorders. In resource-limited settings where kinase enzyme assays are not universally available to patients, web-based mutation prediction tools may be beneficial to predict the deleterious effects of the mutation.
Project description:ObjectiveTo identify the cause of cervical dopa-responsive dystonia (DRD) in a Muslim Indian family inherited in an apparently autosomal recessive fashion, as previously described in this journal.MethodsPrevious testing for mutations in the genes known to cause DRD (GCH1, TH, and SPR) had been negative. Whole exome sequencing was performed on all 3 affected individuals for whom DNA was available to identify potentially pathogenic shared variants. Genotyping data obtained for all 3 affected individuals using the OmniExpress single nucleotide polymorphism chip (Illumina, San Diego, CA) were used to perform linkage analysis, autozygosity mapping, and copy number variation analysis. Sanger sequencing was used to confirm all variants.ResultsAfter filtering of the variants, exome sequencing revealed 2 genes harboring potentially pathogenic compound heterozygous variants (ATM and LRRC16A). Of these, the variants in ATM segregated perfectly with the cervical DRD. Both mutations detected in ATM have been shown to be pathogenic, and α-fetoprotein, a marker of ataxia telangiectasia, was increased in all affected individuals.ConclusionBiallelic mutations in ATM can cause DRD, and mutations in this gene should be considered in the differential diagnosis of unexplained DRD, particularly if the dystonia is cervical and if there is a recessive family history. ATM has previously been reported to cause isolated cervical dystonia, but never, to our knowledge, DRD. Individuals with dystonia related to ataxia telangiectasia may benefit from a trial of levodopa.
Project description:Background:Dystonia is a relatively common feature of spinocerebellar ataxia 3 (SCA3). Childhood onset of SCA3 is rare and typically associated with either relatively large, or homozygous, CAG repeat expansions. Case report:We describe a 10-year-old girl with SCA3, who presented with tongue dystonia in addition to limb dystonia and gait ataxia due to a heterozygous expansion of 84 repeats in ATXN3. Discussion:Diagnosis of the SCAs can be challenging, and even more so in children. Tongue dystonia has not previously been documented in SCA3.
Project description:ObjectiveTo compare the phenotype of primary-appearing dystonia due to variant ataxia-telangiectasia (A-T) with that of other dystonia ascertained for genetics research.MethodsMovement disorder specialists examined 20 Canadian Mennonite adult probands with primary-appearing dystonia, as well as relatives in 4 families with parent-child transmission of dystonia. We screened for the exon 43 c.6200 C>A (p. A2067D) ATM mutation and mutations in DYT1 and DYT6. Clinical features of the individuals with dystonia who were harboring ATM mutations were compared with those of individuals without mutations.ResultGenetic analysis revealed a homozygous founder mutation in ATM in 13 members from 3 of the families, and no one harbored DYT6 or DYT1 mutations. Dystonia in ATM families mimicked other forms of early-onset primary torsion dystonia, especially DYT6, with prominent cervical, cranial, and brachial involvement. Mean age at onset was markedly younger in the patients with variant A-T (n = 12) than in patients with other dystonia (n = 23), (12 years vs 40 years, p < 0.05). The patients with A-T were remarkable for the absence of notable cerebellar atrophy on MRI, lack of frank ataxia on examination, and absence of ocular telangiectasias at original presentation, as well as the presence of prominent myoclonus-dystonia in 2 patients. Many also developed malignancies.ConclusionAtaxia and telangiectasias may not be prominent features of patients with variant A-T treated for dystonia in adulthood, and variant A-T may mimic primary torsion dystonia and myoclonus-dystonia.
Project description:Spinocerebellar ataxia (SCA) is a heterogeneous group of neurodegenerative ataxic disorders with autosomal dominant inheritance. We aim to provide an update on the recent clinical and scientific progresses in SCA where numerous novel genes have been identified with next-generation sequencing techniques. The main disease mechanisms of these SCAs include toxic RNA gain-of-function, mitochondrial dysfunction, channelopathies, autophagy and transcription dysregulation. Recent studies have also demonstrated the importance of DNA repair pathways in modifying SCA with CAG expansions. In addition, we summarise the latest technological advances in detecting known and novel repeat expansion in SCA. Finally, we discuss the roles of antisense oligonucleotides and RNA-based therapy as potential treatments.